The present invention relates to a device for correcting the levels at which book blocks, emerging from a rounding and backing machine, are transferred to a machine downline, the level corrections being referred to a level predetermined by the latter machine.
It is well known that when book blocks undergo the rounding and backing operation, one result is that they emerge with their spines at different levels, and this necessitates a correction for their transfer to a processing machine which is located downline and requires that the spine tops all be at a constant level. This requirement implies that each book block must be raised or lowered by an appropriate, individually determined amount, prior to its acquisition by the transport system of the machine downline.
In known correction devices, use is made of jaws that can be caused to swing, these jaws acting on the side surfaces of the book, in the sense of producing a gripping effect. The throw of this jaw-swinging movement is set by hand, in accordance with a value which is specified in advance, and must therefore be determined. The setting is effected by adjusting a face cam and link motion mechanism that utilizes lever assemblies. The link slot guide associated with known devices is straight, and when it is used, the null, or dead center, point can be determined only by means of a relatively complicated calibration procedure, by reason of the fact that there is no null-point compensation. Determination of the null point is, however, a prerequisite for setting the throw of the jaw-swinging movement.